Field of the Invention
The present invention relates to technology for correcting the image blur or tilt of an image due to shaking.
Description of the Related Art
An image-blur correction apparatus mounted on an imaging apparatus suppresses image blur of an image on an image plane, for example, by moving a lens or an imaging device on a plane perpendicular to an optical axis according to an amount of camera shake. Alternatively, it is possible to suppress image blur caused by roll rotation by rotating the imaging device around an optical axis. Also, there is a tilt correction apparatus for detecting a tilt angle of an apparatus with high precision by detecting the direction of gravity using an acceleration meter or the like and automatically correcting tilt of the imaging apparatus for a horizontal plane perpendicular to the direction of gravity. In the capturing of a moving image, the influence of shake or tilt is reduced by changing a clipping position of each photographing frame output by the imaging device through electronic correction. The imaging apparatus disclosed in Japanese Patent Laid-Open No. H7-95466 corrects tilt around the optical axis for the horizontal plane perpendicular to the direction of gravity of the imaging device by detecting tilt of the imaging apparatus and automatically correcting the tilt in a captured image.
Also, there area charge coupled device (CCD) sensor and a complementary metal oxide semiconductor (CMOS) of low power consumption as the imaging device, and the CCD and the CMOS are different in terms of an exposure scheme during photographing. While exposure timings and exposure periods of all images of the imaging device are the same when one image is captured in the CCD sensor, a difference between exposure periods occurs in the CMOS sensor because the opening/closing timing of a shutter is different for every line constituting the imaging device. In a driving scheme of the CMOS sensor called the rolling shutter scheme, an object image moves for every line of the imaging device, for example, due to movement of an object during exposure or camera shake by a photographer grasping an imaging apparatus during exposure. Thus, a phenomenon in which distortion is caused in a captured image occurs and is referred to as a “rolling shutter problem” or a “focal plane phenomenon.” The rolling shutter distortion is known to be more remarkable in moving-image capturing in which no mechanical shutter is used than in still-image capturing in which a mechanical shutter is used.
In Japanese Patent Laid-Open No. 2006-186481, technology for correcting distortion caused by camera shake by the photographer in relation to correction of rolling shutter distortion is disclosed. An apparatus of Japanese Patent Laid-Open No. 2006-186481 changes a read position for every line of the imaging device to correct the camera shake of the horizontal direction and changes a position of a read line in the vertical direction to correct the camera shake in the vertical direction.
In the case of the imaging apparatus which performs shake correction, tilt correction, or the rolling shutter distortion correction, it is necessary to increase each correction range to increase each correction effect if the amplitude of the shake increases due to the transfer of vibration to the imaging apparatus according to the shake of the body of the user, such as when photographing is performed while walking.
There are optical correction and electronic correction as types of image-blur correction. The optical correction is optical-axis shift correction for moving a part of a lens of an imaging optical system or an imaging device in a shift direction, correction of rotationally driving a barrel in which the lens and the imaging device are integrated on the basis of a shake angle, or the like. In the case of mechanical correction, it is necessary to perform correction in a translation direction (a vertical direction and a horizontal direction of an image) and correction of a roll direction within a limited movable range. On the other hand, in the electronic correction, the correction is performed through image processing by changing a clipping position of each photographing frame. In this case, it is possible to reduce a clipping range for an original image and enlarge a correction range by allocating a surplus of an image to correction ranges of translation, roll, and rolling shutter distortion. However, when an angle of view of clipping of the image is excessively reduced, there is a possibility of image deterioration occurring due to degradation of resolution or an event of reduction of an angle of view of photographing after clipping.